Data center solutions have been aggressively adopting Layer 2 (L2) based architectures to solve interconnectivity problems and provide new services to users. Standard Layer 2 forwarding models do not enable multiple active links to forward Layer 2 traffic between interconnected network devices, and typically block all but one link to forward data in scenarios where multiple links connect two network devices. New Layer 2 overlay technologies, such as Ethernet Virtual Private Network (EVPN), introduce new forwarding models that need multi-homing forwarding in which two network devices are coupled through a plurality of links. These models propose that network devices operate in either an all-active mode, where all links are active, or in a single-active mode (where a single one of the links is active and the other links are in a standby status). The L2 overlay deployments further mandate the support of failure detection mechanisms and re-route of the associated L2-destinations over alternate paths. The failure detection and reroute mechanism need to scale well to avoid increased long convergence times of the control plane (in reroute cases) when L2 and Layer 3 technologies are used in combination (e.g., as proposed in EVPN).
In scenarios where a network device is multi-homed, load spreading among links that can reach the multi-homed L2 destination is not possible with current technologies. In addition, in technologies such as Virtual Private LAN Service (VPLS) a Layer 2 destination address (e.g., a Media Access Control (MAC) address) can only be learned over one pseudo-wire and hence use of multiple links is not feasible where the destination is multi-homed in a VPLS environment.
Existing Layer 2 overlay solutions do not support use of multiple paths to reach active L2 destinations. In addition, current solutions do not permit the configuration of a primary path and a set of alternate paths to reach a given L2 destination. Further, in a case of failure within the path towards the L2 destination, the existing reroute mechanisms result in the update of the routes to each L2 destination in the forwarding plane. However, an update per L2 destination can cause severe synchronization and convergence delays in the network.